Rechargeable lithium batteries operating at room temperature offer several advantages compared to conventional aqueous technologies. These advantages include higher energy density, (up to 150 watt-hrs per kilogram), higher cell voltage (up to about 4V per cell), and longer charge retention or shelf life (up to 5-10 years). These advantageous characteristics result in part from the high standard potential and low electrochemical equivalent weight of lithium. A variety of materials have been investigated for the use as electrodes, such as intercalation solid compounds, soluble and polymeric materials. Liquid aprotic organic solvents containing dissolved inorganic salts are used as electrolytes in many cells. Solid polymer electrolytes are also popular as they may provide a safer design because of their lower reactivity with lithium.
Rechargeable lithium batteries have been introduced into the market on a limited scale. Coin cells using lithium-aluminum anodes are available for special applications mainly for low-power portable applications where they can be conveniently recharged, and in some instances by solar cells. More recently, the lithium ion cell, which has a potential safety advantage over other lithium secondary cells as it does not contain lithium in a metallic form has been marketed as a power source for consumer electronics such as cellular telephones and camcorders.
The rechargeable lithium ion polymer cells, which use solid polymer electrolytes, are considered to have a safety advantage over the lithium ion cells because of their lower reactivity with lithium, and in having low concentration of volatile and often flammable organic solvents. In their most common form, these cells use a lithium-ion conducting polymer membrane which acts both as the electrolyte and as the separator, a thin-lithium metal foil or carbon based material as the negative or anode material, and a transition metal oxide or chalcogenide such as V.sub.2 O.sub.5, TiS.sub.2 or V.sub.6 O.sub.13 blended with carbon and backed by metal foil current collector as a positive electrode.
Polymer electrolyte battery cells are often packaged in a flexible container consisting of metallized foil and several layers of a special polymer. Gas formation due to electrolyte decomposition during initial cycling is very common in polymer cells. Getting rid of these gases is very tedious. Therefore there is a need for an improved flexible metal foil packaging for a polymer battery cell that would make this tedious and time consuming operation easy.